U.S. Patent Publication No. 2002/070023 (“Turner et al.) discloses a completion string including a base pipe having a hole, a packer in mechanical communication with the base pipe, and an isolation pipe concentric with the base pipe and proximate to the hole in the base pipe, with an annulus defined between the base pipe and the isolation pipe. An annulus-to-annulus valve is in mechanical communication with the base pipe and isolation pipe.
U.S. Patent Publication No. 2003/0178198 (“Turner et al.) discloses an isolation string having an upper packer and an isolation pipe in mechanical communication with the upper packer. The isolation pipe a pressure activated valve and an object activated valve.
U.S. Pat. No. 4,534,426 (“Hooper”) shows a tool including a drill bit in combination with an expansible packer means for sealing with the well bore above the bit and fluid circulating means.
U.S. Pat. No. 4,296,807 (“Hendrickson et al.”) shows a crossover tool for use with concentric tubing strings. The crossover tool is run into the well on the end of a drill pipe. The crossover tool includes a body about which a sleeve is slidably disposed. Movement of the outer sleeve by reciprocating the drill pipe changes the mode of operation of the crossover tool.
U.S. Patent Publication No. 2006/0045757 (“Parr”) shows a production tool in which a packer is attached to a tubing string so that the well bore is divided into two annular spaces. Compressed gas is introduced into the annular space above the packer. There is the possibility of communication between the two spaces on either side of the packer in that the tubing is provided with holes for passage of fluid into its interior.
U.S. Pat. No. 3,638,742 (“Wallace”) shows a dual string with an annular seal mounted between the dual string and the well bore wall.
U.S. Pat. No. 5,526,887 (“Vestavik”) discloses a piston mounted on a drill string and adapted to form a sliding seal against the wall of borehole. A seal is arranged between the wall of the borehole and the drill string and above the piston. A pipe extends from a pressure-controlled pump, through the seal, into a volume between the seal and piston. Fluid can be pumped into the volume to exert pressure on the piston, which will urge the drill string against the bottom of the borehole. A return line extends from below the piston, through holes in the piston and seal, to the surface.
U.S. Pat. No. 5,044,432 (“Cunningham et al.”) discloses a well pipe hanger with a metal sealing annulus valve.